package com.jdaw.algorithm.floyd;

import java.util.Arrays;

public class FloydAlgorithm {
    public static void main(String[] args) {
        char[] vertex = { 'A', 'B', 'C', 'D', 'E', 'F', 'G' };
        int[][] matrix = new int[vertex.length][vertex.length];
        final int N = 65535;
        matrix[0] = new int[] { 0, 5, 7, N, N, N, 2 };
        matrix[1] = new int[] { 5, 0, N, 9, N, N, 3 };
        matrix[2] = new int[] { 7, N, 0, N, 8, N, N };
        matrix[3] = new int[] { N, 9, N, 0, N, 4, N };
        matrix[4] = new int[] { N, N, 8, N, 0, 5, 4 };
        matrix[5] = new int[] { N, N, N, 4, 5, 0, 6 };
        matrix[6] = new int[] { 2, 3, N, N, 4, 6, 0 };
        //创建 Graph 对象
        Graph graph = new Graph(vertex.length, matrix, vertex);
        graph.floyd();
        graph.show();
    }
}

class Graph{
    private char[] vertex;//存放顶点数组
    private int[][] dis;
    private int[][] pre;//到达目标顶点的前驱结点

    public Graph(int length, int[][] matrix, char[] vertex) {
        this.vertex = vertex;
        this.dis = matrix;
        this.pre = new int[length][length];
        // 对pre数组初始化, 注意存放的是前驱顶点的下标
        for (int i = 0; i < length; i++) {
            Arrays.fill(pre[i], i);
        }
    }

    // 显示pre数组和dis数组
    public void show() {

        //为了显示便于阅读，我们优化一下输出
        char[] vertex = { 'A', 'B', 'C', 'D', 'E', 'F', 'G' };
        for (int k = 0; k < dis.length; k++) {
            // 先将pre数组输出的一行
            for (int i = 0; i < dis.length; i++) {
                System.out.print(vertex[pre[k][i]] + " ");
            }
            System.out.println();
            // 输出dis数组的一行数据
            for (int i = 0; i < dis.length; i++) {
                System.out.print("("+vertex[k]+"到"+vertex[i]+"的最短路径是" + dis[k][i] + ") ");
            }
            System.out.println();
            System.out.println();

        }

    }

    public void floyd(){
        int len=0;//保存距离
        for(int k=0;k<dis.length;k++){//中间顶点的遍历
            for(int i=0;i<dis.length;i++){//起点i开始{ 'A', 'B', 'C', 'D', 'E', 'F', 'G' }
                for(int j=0;j<dis.length;j++){
                    len=dis[i][k]+dis[k][j];
                    if(len<dis[i][j]){
                        dis[i][j]=len;
                        pre[i][j]=pre[k][j];
                    }
                }
            }
        }
    }
}